1. Field of the Invention
The present invention relates to magnetic resonance technology, and more particularly, to a receiver coil array used in the magnetic resonance imaging system and a magnetic resonance imaging system comprising said receiver coil array.
2. Description of the Prior Art
In the magnetic resonance imaging system, the receiver coil is used to receive the magnetic resonance signals. A plurality of receiver coils can be arranged in an array and receive magnetic resonance signals through the array to increase the signal-to-noise ratio of the received magnetic resonance signals and better meet the needs of clinical applications. In this case, each of the receiver coils in the receiver coil array can be called a coil unit of the array.
It has become a development trend of the magnetic resonance imaging system to add more coil units in the coil array to improve the quality of the signals received as the needs of clinical application grow. However, coupling may occur among the coil units in the same array thereby changing the frequency (which is determined by pre-tuning) of these coil units to reduce the signal receiving sensitivity of the coils and increase the noise correlation among the coil units, thus reducing the signal-to-noise ratio of the receiver.
In order to solve the aforesaid problems induced by coupling, the prior art adopted the solution of overlapping the coil units of the receiver coil array. FIG. 1 is a schematic diagram showing the structure of a 2×3 receiver coil array using the overlapping coil units. As shown in FIG. 1, taking a 2×3 receiver coil array as an example, each coil unit 10 in the receiver coil array comprises a PCB 11 as the output regulation circuit which is used to regulate the frequency and impedance of the coil unit 10 (that is, the PCB 11 is pre-tuned to determine the frequency and impedance of the coil unit 10 on which the PCB 11 is located), and amplify and output the magnetic resonance signals received by the coil unit 10 on which it is located (shown by the arrow head in FIG. 1); each coil unit 10 is overlapped with the adjacent coil units to enable the overlapping edge of the adjacent coil units to play the role of a decoupling capacitor. However, the solution of overlapping coil units as shown in FIG. 1 causes very complicated relationships among the coil units in the entire receiver coil array and it is difficult to determine the reasonable overlapping area between the coil units.
Therefore, the prior art further adopted a solution of using a decoupling capacitor in the receiver coil array. FIG. 2 is a schematic diagram illustrating the structure of a 2×3 receiver coil array using a decoupling capacitor. As shown in FIG. 2, taking a 2×3 receiver coil array as an example, each coil unit 10 in the receiver coil array shares a common side 21 with each of the adjacent coil units and each common side 21 has a capacitor 22 on it. Since coil unit 10 can be treated as a resonance circuit consisting of an inductor and capacitor, once the size of the coil unit 10 is determined, the inductance value of said coil unit 10 can be determined. At this point, regulation of the frequency and impedance of the coil unit 10 can be achieved by adjusting the value of the capacitor 22 on the common side 21 to reduce the effect of the coupling between the coil units on the frequency of the coil units. In which case, it is possible to adjust the value of the capacitor 22 by connecting a plurality of capacitors in series or in parallel. As with the solution shown in FIG. 1, there is a PCB 11 set on the non-common side of each coil unit 10 shown in FIG. 2 to regulate the frequency and impedance of the coil unit 10 and to amplify and output the magnetic resonance signals received by the coil unit 10 on which it is located (shown by the arrow head in FIG. 2).
The solution of using a decoupling capacitor does not complicate the relationship between the coil units in the receiver coil array and can reduce the effect of the coupling between the coil units on the frequency of these coil units. However, the solution is only applicable to a receiver coil array comprising only a small number of coil units.
FIG. 3 is a schematic diagram showing the structure of a 3×3 receiver coil array with a capacitor decoupling solution. As shown in FIG. 3, taking a 3×3 receiver coil array as an example, each coil unit in the receiver coil array shares a common side 21 with each of the adjacent coil units and each common side 21 has a capacitor 22 on it. There is a PCB 11 on the non-common side of the eight coil units 10 in the periphery (referred to as peripheral coil units) for regulating the frequency and impedance of the coil unit 10 and amplifying and outputting the magnetic resonance signals received by the coil unit on which it is located (shown by the arrow head in FIG. 3). All sides of the middle coil unit 30 surrounded by the eight peripheral coil units 10 are common sides 21 with the peripheral coil units 10 (the middle coil unit mentioned hereinafter means a coil unit, all sides of which are common sides), that is, all sides of the middle coil unit 30 are provided with a capacitor 22 for decoupling making it impossible to further install a PCB to regulate the frequency of said coil unit and the magnetic resonance signals received by the middle coil unit 30 cannot be outputted as well, or in other words, only the eight peripheral coil units 10 in the receiver coil array shown in FIG. 3 can output the received magnetic resonance signals.
It is evident that the prior art includes a greater number of coil units in the receiver coil array and when the aforementioned middle coil unit is included, it is impossible to regulate the frequency of the coil units and to output the magnetic resonance signals received by the coil units, and this is equivalent to reducing the number of coil units in the receiver coil array that are capable of receiving and outputting the magnetic resonance signals, hence the reduction in the quality of the signal received by the receiver coil array.